This is an issue I've never been quite sure where I stand on. But keep in mind that it's not about tearing the system down (for me anyway). It's simple: the current system is an ineffective joke. My vote doesn't matter beyond at best the county level. So, I refuse to participate. Period. Rational egoism does not necessarily dictate that I take the next step and fight for change -- that's where your critique fails to apply.
So, when you say that "passive protest does absolutely nothing" ... well, not to me. If you insist that not voting has to be an act of protest, I can only say -- fine. The system is stupid and voting isn't at the moment compulsory; thus I will live out a few more years and then move to a better country. My country has no claim on me at all. Voting stopped being a 'civic duty' long before I was born.